"...appear reasonably sharp (according to the standards of sharpness required for the particular photograph and the degree of enlargement of the negative)."

"...distances within which objects are imaged with acceptable sharpness."

"...which will also be acceptably sharp."

DoF is not a mathematical formula; it is a perceived value. You can mathematically model DoF any way you like, but you cannot use a model to evaluate the influence of a variable if your model ignores that variable.

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Some would have you believe that having to adapt to new technology is a workaround, but having adapted to old technology is photography.